Powder Electrodes Research Articles

Modeling of the chemical composition of the layer fused with a powder electrode

Problem. The work is devoted to the problem of the formation of high-quality deposited metal during the restoration of parts of small diameters with insignificant dimensions of wear. Goal. The purpose of the work is the development of a mathematical model for calculating the composition of metal deposited by flux-cored wire with forced transfer of the electrode metal. Methodology. The composition of the core of the powder electrode should ensure protection of the deposited metal from the action of air, ensure alloying of the metal, its deoxidation, high-quality formation of the bead, easy separation of the slag crust, minimal splashing of the molten metal, the absence of pores, cracks, and slag inclusions in the deposited layer. However, a number of surfacing self-protecting powder electrodes contain a significant amount of gas-slag-forming components in the charge. The result can be: failure of the rollers to fuse with each other and with the base metal, loss of alloying elements due to oxidation, slagging of the rollers, and slag runoff. In order to ensure the specified chemical composition of the deposited metal, a mathematical model for calculating the composition of a layer deposited by a powder electrode with forced metal transfer has been developed, which id correctly taken into account during the configuration of the rollers relative to each other and relative to the base metal. Results. The influence of the deposition step and the coefficient of reinforcement of the deposited roll on the value of the share of the metal of the previous roll of the deposited layer in the next roll was determined. The influence of the surfacing step on the quality of the formation of the surfacing layer was determined experimentally. Practical value. Technological recommendations have been developed and proposed for applying a layer with powder electrodes with forced metal transfer, which ensure high quality of the deposited metal with the formation of a layer of the required chemical composition. It was established that if the recommendations regarding the technological parameters of the process are followed, the necessary chemical composition of the deposited metal is achieved already in the second layer.

3D network of zinc powder woven into fibre filaments for dendrite-free zinc battery anodes

Zinc foil metal anodes in aqueous zinc ion batteries (AZIBs) are impaired by uncontrollable dendrite growth, resulting in low Coulombic efficiency (CE) and limited lifetime. The tunability of zinc powder provides a perfect alternative for anodes. But their rough spherical surfaces possibly make them more susceptible to corrosion and dendrite growth. We hereby utilise electrostatic spinning to weave zinc powder into polyacrylonitrile/ Polyvinylidene fluoride (PVDF/PAN) fiber filament to produce a new three-dimensional porous zinc anode (PF@Zn). Stable and flexible structure of the constructed fiber filament framework avoids direct contact of the aqueous electrolyte with the collector while relieving the stresses generated by dendrite growth. Moreover, when galvanizing or stripping, the zinc powder woven into the fiber network efficiently homogenizes the Zn2+ ion flux for a stable zinc cycle. Accordingly, the PF@Zn anode battery has a superior cycle life (240 h) and an increased Coulombic efficiency (99.1 %). An assembled C//PF@Zn capacitor has an impressive 96.6 % capacity retention after 3000 cycles. The study offers a scalable approach to modifying metal powder electrodes and transforming them into high-performance batteries.

In-situ fabrication of Na3V2(PO4)3/C thin-film electrode for high-performance sodium-ion batteries

Compared with the traditional powder electrode, the active material/carbon composite thin-film electrode has many advantages in binder-free, flexible and electrochemical performance. However, typical fabrication methods of film electrodes, such as chemical vapor deposition (CVD) and physical vapor deposition (PVD), are complex and costly. Herein, an accessible and economical spin-coating method is proposed to in-situ fabricate Na3V2(PO4)3 film with different thicknesses on graphite discs, whose electrochemical performances are investigated in sodium-ion batteries. The results show that a specific capacity of 167 mA h g−1 at 1 C is obtained in the thinner electrode thanks to the contribution of the graphite substrate. It is also found that the specific capacity of the electrode decreases as the film becomes thicker while the cycling stability and electrochemical kinetics are significantly improved. The capacity retention of 93.8 % is achieved in the thicker electrode after 5000 cycles at 10 C. This work presents a novel idea for designing and building high-performance, economical, and environmentally friendly energy storage devices.

Al‐doped ZnO‐Coated LiNi1/3Mn1/3Co1/3O2 Powder Electrodes: The Effect of a Coating Layer on The Structural and Chemical Stability of The Electrode / Electrolyte Interface

AbstractLiNi1/3Mn1/3Co1/3O2 (NMC‐111) is one of the most popular cathode materials in Li‐ion batteries. However, chemical and structural instabilities of the cathode/electrolyte interface at high charge cut‐off voltages cause capacity fading. Surface modifications using metal oxides are promising candidates to suppress capacity fading. Here a systematic study on the degradation mechanism of an uncoated NMC‐111 powder electrode is presented. Moreover, the effect of an Al‐doped ZnO (Al:ZnO) coating layer on the structural and chemical stabilities of NMC‐111 electrode cycled at high charge cut‐off voltages is analyzed using X‐ray photoelectron spectroscopy, scanning electron microscopy and analytical transmission electron microscopy as well as electrochemical testing. The coating is applied to commercial NMC‐111 powder using a microwave‐assisted sol‐gel synthesis method. In the case of uncoated NMC‐111 electrodes, pitting corrosion due to hydrofluoric acid attacking the electrode surface, cation mixing, and an irreversible phase transformation from a trigonal layered to a rock‐salt phase occurs, causing capacity fading. While, in the case of Al:ZnO – coated NMC‐111 electrodes, pitting corrosion, cation mixing, and the irreversible phase transformation are mitigated. Therefore, the capacity retention and rate capability are improved as the coating layer protects the electrode surface from the direct electrolyte exposure.

Upcycling electrode materials from spent single-use zinc‑carbon/alkaline batteries into rechargeable lithium-ion battery application

Battery recycling/upcycling is a key component of modern e-waste reduction by transforming discarded electrode powder to value-added materials and chemical feedstocks for the proposed applications. In this study, electrode powder from spent zinc‑carbon/alkaline batteries was upcycled into LiMn2O4 cathode and carbon anode for rechargeable lithium-ion battery. The main metallic contents (zinc and manganese) in electrode powder were quantitatively leached using diluted H2SO4 with the presence of H2O2 as a reducing agent. By applying sequential precipitation, ZnS nanospheres and MnCO3 nanocubes were obtained as determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The recovered MnCO3 was heated with a stoichiometric amount of Li2CO3 to produce high crystalline and pure LiMn2O4. For the electrochemical performance, the results show that upcycled LiMn2O4 exhibits initial discharge capacity of 99.0 mAh g−1 for zc-LiMn2O4 and 111.0 mAh g−1 for al-LiMn2O4, compared to 90.4 mAh g−1 for pristine LiMn2O4. Moreover, recovered carbon materials obtained as an insoluble powder after acid leaching possess unique morphology and crystallinity. The zc‑carbon shows superior cycling performance with reversible charge capacity of 552 mAh g−1 at 1C rate after 100 cycles. This study provides the great potential for upcycling waste battery electrodes to high-value LiMn2O4 cathode and carbon anode for lithium-ion battery application.

Electrochemical Sodium Storage in Hard Carbon Powder Electrodes Implemented in an Improved Cell Assembly: Insights from In-Situ and Ex-Situ Solid-State NMR.

In this work, we report on an improved cell assembly of cylindrical electrochemical cells for 23 Na in-situ solid-state NMR (ssNMR) investigations. The cell set-up is suitable for using powder electrode materials. Reproducibility of our cell assembly is analyzed by preparing two cells containing hard carbon (HC) powder as working electrode and sodium metal as reference electrode. Electrochemical storage properties of HC powder electrode derived from carbonization of sustainable cellulose are studied by ssNMR. 23 Na in-situ ssNMR monitors the sodiation/desodiation of a Na|NaPF6 |HC cell (cell 1) over a period of 22 days, showing high cell stability. After the galvanostatic process, the HC powder material is investigated by high resolution 23 Na ex-situ MAS NMR. The formation of ionic sodium species in different chemical environments is obtained. Subsequently, a second Na|NaPF6 |HC cell (cell 2) is sodiated for 11 days achieving a capacity of 220 mAh/g. 23 Na ex-situ MAS NMR measurements of the HC powder material extracted from this cell clearly indicate the presence of quasi-metallic sodium species next to ionic sodium species. This observation of quasi-metallic sodium species is discussed in terms of the achieved capacity of the cell as well as of side reactions of sodium in this electrode material.

In-situ growth of electrically conductive MOFs in wood cellulose scaffold for flexible, robust and hydrophobic membranes with improved electrochemical performance

Electrically conductive metal-organic frameworks (EC-MOFs) have attracted great attentions in electrochemical fields, but their practical application is limited by their hard-to-shape powder form. The aims was to integrate continuously nucleated EC-MOFs on natural wood cellulose scaffold to develop biobased EC-MOFs membrane with robust flexibility and improved electrochemical performance for wearable supercapacitors. EC-MOF materials (NiCAT or CuCAT) were successfully incorporated onto porous tempo-oxidized wood (TOW) scaffold to create ultrathin membranes through electrostatic force-mediated interfacial growth and simple room-temperature densification. The studies demonstrated the uniform and continuous EC-MOFs nanolayer on TOW scaffold and the interfacial bonding between EC-MOF and TOW. The densification of EC-MOF@TOW bulk yielded highly flexible ultrathin membranes (about 0.3 mm) with high tensile stress exceeding 180 MPa. Moreover, the 50 %-NiCAT@TOW membrane demonstrated high electrical conductivity (4.227 S·m−1) and hydrophobicity (contact angle exceeding 130°). Notably, these properties remained stable even after twisting or bending deformation. Furthermore, the electrochemical performance of EC-MOF@TOW membrane with hierarchical pores outperformed the EC-MOF powder electrode. This study innovatively anchored EC-MOFs onto wood through facile process, yielding highly flexible membranes with exceptional performance that outperforms most of reported conductive wood-based membranes. These findings would provide some references for flexible and functional EC-MOF/wood membranes for wearable devices.

GH3536 superalloy prepared by selective laser melting: microstructure and properties

In this paper, GH3536 superalloy was prepared by selective laser melting (SLM) using plasma rotating electrode powder as raw material. The effects of forming and heat treatment processes on the microstructure and mechanical properties of GH3536 superalloy were studied. The results show that there were obvious micro-cracks on the laser scanning plane of SLM samples, and the length of micro-cracks was between 10-100μm. The micro-cracks originated from the inside of the molten pools and penetrated the melting channels, and the heat treatment could not eliminate the cracks. With the increase of volume energy density (VED), the tensile strength and yield strength of SLM samples increased first and then decreased. The maximum values of tensile strength and yield strength reached 772.3MPa and 613.3MPa, respectively. However, with the increase of VED, the elongation of SLM samples decreased to 27.3%. After heat treatment, the tensile strength and yield strength of the material increased (up to 789MPa and 410MPa), but the elongation decreased.

Metal Carbide Additives in Graphite‐Silicon Composites for Lithium‐Ion Batteries

AbstractThe pathway for improving lithium‐ion batteries′ energy density strongly depends on finding materials with enhanced performance. Although great efforts have been done, on the anode‐side, graphite is still the best choice. In the last decade, silicon elements are attracting growing attention as anode since their use can theoretically increase specific capacity of the negative electrode side. However, as the electrochemical mechanism involves the alligation of a large amount of Li, the silicon electrode experiences huge volume changes (more than 300 % of its initial volume), leading to fractures and pulverizations of the electrode. Herein, we propose for the first time using Molybdenum and Chromium Carbides as additive to stabilize graphite/silicon composites. Spark plasma sintering technology is used to sinter the electrode powders. We demonstrated that the presence of molybdenum or chromium carbides promotes the performance of C/Si electrodes, improving the cycling stability compared to pristine graphite/silicon electrodes.

A Novel Procedure for Comprehensive Recovery of Zinc Fluoride, Manganese Fluorides, Manganese Dioxide, and Carbon Powder from the Electrode Powder of Spent Alkaline Batteries

A Novel Procedure for Comprehensive Recovery of Zinc Fluoride, Manganese Fluorides, Manganese Dioxide, and Carbon Powder from the Electrode Powder of Spent Alkaline Batteries

(Invited) 2D Mxenes for Energy Storage Applications

MXenes are a family of two-dimensional (2D) transition metal carbides and nitrides, with a general structure of Mn+1XnT x , where M is the transition metal, X is carbon and/or nitrogen, and T represents the surface terminations (F, O, OH). MXenes have attracted attention in a multitude of energy storage applications due to their high electronic conductivity, tunable interlayer spacing, redox-active transition metals, and hydrophilic surface groups. In this talk, we discuss the use of MXene electrodes in supercapacitor applications, including aqueous, non-aqueous, and water-in-salt electrolytes. The variability of MXenes is demonstrated with each electrolyte system showing unique electrochemical responses, not limited to redox and/or intercalation pseudocapacitance, and hydrated cation intercalation. Furthermore, the versatility of the hydrophilic, 2D morphology of MXenes is demonstrated through its use in multiple form factors, not limited to flexible free-standing films, multilayer powder electrodes, interdigitated microsupercapacitors, knitted textiles, and more. New directions and perspectives for MXenes in energy storage are discussed, including MXenes’ use as passive components (separators, current collectors, binders, scaffolds, conductive additives) in energy storage systems. Figure 1 (A) Schematic illustration showing MXenes’ electrochemical properties for ion storage applications. (B) Cyclic voltammetry (CV) data collected at scan rates from 10 to 100,000 mV·s−1 for a 90-nm-thick Ti3C2T x film. (C) Influence of an electrolyte’s solvent on the lithium-ion storage capacity of Ti3C2T x ; CV curves of microporous Ti3C2T x electrode in 1 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in DMSO, acetonitrile (ACN), or propylene carbonate (PC) electrolytes. (D) A digital photograph showing the wafer scale fabrication of an array of 143 MXene microsupercapacitors. (E) Photograph of a knitted textile with an interdigitated pattern made using Ti3C2T x MXene-coated cotton yarn to produce electrodes for wearable textile supercapacitor.Reference[1] A. VahidMohammadi, J. Rosen, Y. Gogotsi, Science, 2021, 372, eabf1581. Figure 1

(Invited) Nanoscale Surface Coatings for High-Performance Nickel-Rich LiNixMnyCozO2 Cathodes Via Atomic Layer Deposition

Nickel (Ni)-rich LiNixMnyCozO2 (NMCs, x + y + z = 1, x ≥ 0.6) are among the most promising cathodes for next-generation lithium-ion batteries (LIBs) and beyond, ascribed to their high capacity and low cost. With increasing Ni contents, however, NMCs become more challenging for commercialization, due to a series of aggravated issues. In addressing these issues, surface coating has been remaining as a facile and effective strategy. In this regard, atomic layer deposition (ALD) has been recognized as a unique surface-coating technique in the past decade, featuring its unrivaled capability for uniform and conformal coatings.1-3 ALD also is to date the only technique that can perform on either prefabricated electrodes or electrode powders directly. In searching for new solutions to the issues of NMCs, recently we have conducted a series of studies on different coatings, including oxides and sulfides via ALD.4-8 Our studies revealed that Li-containing oxides are better than Li-free oxides, due to improved ionic conductivity. They both served multiple roles for protecting NMCs, including as a physical barrier to mitigate undesirable interfacial reactions, a structural stabilizer to inhibit unfavorable phase transformation, and a robust network to improve mechanical integrity. Very interestingly, we for the first time have discovered that, compared to oxide coatings, sulfides are more advantageous. Our studies have revealed that, while acting similar roles as oxides, sulfides have some unusual protection effects for better performance of NMCs. We found that sulfides could experience some favorable phase transition during charge-discharge processes, which transferred sulfides into sulfites or/and sulfates. This transition process could particularly remove the released oxygen from NMCs and thereby protected electrolytes from oxidation. We further demonstrated that this transition is significant for achieving long-term stable cyclability of NMCs. Thus, our studies have greatly widened the search of surface coatings and provided new solutions for next-generation LIBs and beyond.

Influence of A-site Deficiency and Ni/Co Ratio in B-site on Electrochemical Performance of (La0.25Sr0,25Ca0.45)yTi0.95Ni0.05-xCoxO3- d Anode

La0.25Sr0.25Ca0.45TiO3 -d (LSCT) is a perovskite (ABO3) type mixed ionic-electronic conductive (MIEC) oxide and has been proposed as an electrode material for high temperature fuel cell [1]. This material owing high conductivity, robustness in hydrocarbon fuels and significant amount of attention has been paid to improve the electrochemical activity [1, 2]. Doping of B-site with some d-metal cation (Ni, Co, Mn, V, Mo) has been demonstrated to improve the catalytic activity. One of the advantages of the MIEC conducting scaffold based electrodes is that the catalyst phase on the electrode surface can be kept to a minimum, usually less than 5 wt%, which minimizes any risks of physical damage during redox cycling [2].In this work, Ni/Co ratio and deficiency of A-site, of (La0.25Sr0.25Ca0.45)xTi0.95Ni0.05-yCoyO3 -d were varied. Electrical as well as electrochemical performance and chemical composition of LSCTNC surface was monitored. The electrochemical measurements of symmetric cells during 100 h tests show that small stochiometric changes in A-site significantly influence the activity and initial degradation rate of the electrode. The chemical and structural changes of the material surface have a key role on the electrochemical performance of the electrode [3].The electrode materials were analysed using XRD, TOF SIMS and electrochemical methods. XRD and TOF SIMS results for studied electrode powders showed significant dependence of the lattice parameters and electrode surface composition on the perovskite elemental composition. The results from impedance spectroscopy (measured at temperatures from 973 to 1123 K in H2 environment, at OCV) demonstrate a significant influence of the A-site deficiency and B-site composition on the electrochemical properties of studied electrodes. Robert Price, Mark Cassidy, Jan G. Grolig, Gino Longo, Ueli Weissen, Andreas Mai, John T. S. Irvine, Advanced Energy Materials, 11, 1 (2021). Paul A. Connor, Xiangling Yue, Cristian D. Savaniu, Robert Price, Georgios Triantafyllou, Mark Cassidy, Gwilherm Kerherve, David J. Payne, Robert C. Maher, Lesley F. Cohen, Rumen I. Tomov, Bartek A. Glowacki, Ramachandran Vasant Kumar, John T. S. Irvine, Advanced Energy Materials, 8, 1 (2018). Ove Korjus, Priit Möller, Kuno Kooser, Tanel Käämbre, Olga Volobujeva, Jaak Nerut, Sander Kotkas, Enn Lust, Gunnar Nurk, Journal of Power Sources, 494, 1 (2021).

Pr‐ and Co‐substitution in rare earth nickelates: Application as SOEC air electrodes

AbstractIn this work, fundamental material properties of compounds in the system (La,Pr)2(Ni,Co)O4+δ as well as their performance as air electrodes in solid oxide electrolysis cells were investigated. Nickelates co‐doped with Pr and Co were characterized on a material basis by means of X‐ray diffraction and thermogravimetry. Conductivity and conductivity relaxation measurements were performed in order to obtain the electronic conductivity as well as the chemical surface exchange coefficient and the chemical diffusion coefficient of oxygen as a function of temperature and oxygen partial pressure. These parameters can be regarded as the most essential properties at the material level required to assess the suitability of mixed ionic‐electronic conducting ceramics for application as air electrode in solid oxide cells. The electrode performance of the materials was then tested on fuel electrode‐supported button cells at 800°C. The electrodes were applied by screen‐printing and the effect of varying the Pr‐content and Co‐content of the electrode powder was investigated. Cell tests were performed by means of current‐voltage measurements in electrolysis mode. While no significant impact of Pr‐doping on the investigated material properties was observed, the electrode performance of Pr‐containing materials was significantly better than for the Pr‐free compound, which has been discussed in detail.

Characterizations and Inkjet Printing of Carbon Black Electrodes for Dielectric Elastomer Actuators.

Dielectric elastomer actuators (DEAs) have been proposed as a promising technology for developing soft robotics and stretchable electronics due to their large actuation. Among available fabrication techniques, inkjet printing is a digital, mask-free, material-saving, and fast technology, making it versatile and appealing for fabricating DEA electrodes. However, there is still a lack of suitable materials for inkjet-printed electrodes. In this study, multiple carbon black (CB) inks were developed and tested as DEA electrodes inkjet-printed on acrylic membranes (VHB). Triethylene glycol monomethyl ether (TGME) and chlorobenzene (CLB) were selected to disperse CB. The inks' stability, particle size, surface tension, viscosity, electrical resistance, and printability were characterized. The DEA with Ink-TGME/CLB (mixture solvent) electrodes obtained 80.63% area strain, a new benchmark for the DEA actuation with CB powder electrodes on VHB. The novelty of this work involves the disclosure of a new ink recipe (TGME/CLB/CB) for inkjet printing that can obtain stable drop formations with a small nozzle (17 × 17 μm), high resolution (∼25 μm, approaching the limit of drop-on-demand inkjet printing), and the largest area strain of DEAs under similar conditions, distinguishing this contribution from the previous works, which is important for the fabrication and miniaturization of DEA-based soft and stretchable electronics.

Effects of dry powder mixing on electrochemical performance of lithium-ion battery electrode using solvent-free dry forming process

This research examines how the morphology of the electrode powder mixture affects the structure and battery performance of lithium-ion battery electrodes fabricated using a dry electrode forming process. We demonstrate that the distribution of conductive and binding additives (CBA) on the active materials (AMs) can be controlled by adjusting the rotation speed of a dry mixer. Furthermore, we show that controlling the distribution of CBA can improve the rate performance of the batteries. The tortuosity of the CBA domain in the electrodes is analyzed from SEM images of electrode cross-sections as electronic and ionic conductive pathways. Low rotation speed dry mixing results in poor dispersion of CBA, leading to the formation of long-range conductive pathways with low tortuosity. Consequently, the capacity at high rates decreases due to fewer short-range conductive pathways between the AM particles. In contrast, high rotation speed dry mixing leads to excessive dispersion of CBA, resulting in high tortuosity in both long-range and short-range conductive pathways. As a result, the capacity decreases due to fewer efficient conductive pathways throughout the electrode. We demonstrate that medium rotation speed dry mixing achieves a favorable balance between short-range and long-range conductive pathways, providing high capacity at high rates.

Polydopamine-engineered design of Nafion-free powder electrode with superhydrophilicity/superaerophobicity and superior adhesive structure for efficient overall water splitting

Absolute exploitation on the intrinsic catalytic property of powder electrocatalysts always faces the obstacles caused by the existing gas–liquid-solid three-phase interface problem and overwhelming dependence on Nafion usage. Herein, a general polydopamine (PDA)-engineering method is developed to construct Nafion-free powder electrode for efficient overall water splitting. The several nanometer scale PDA coating layers that are self-polymerized on catalyst surfaces, enable the superhydrophilicity/superaerophobicity for more exposed electroactive sites and smoother interfacial mass transfer, and meanwhile, render a superior structural stability inside working electrode with equivalent but more homogeneous adhesion compared with that of Nafion-used electrode. At 300 mA cm−2, the CoMoSxOy@PDA exhibits the low overpotential of 311 mV for OER and 343 mV for HER, and meanwhile demonstrates a cell voltage of only 1.89 V for over 200 h of stable operation and almost unaffected catalytic activity even under harsh ultrasonic working conditions. By theory calculations, the reduced reaction energy barrier for oxygen evolution and the optimized adsorption free energy for hydrogen evolution are revealed in depth.

Conquering poor reversibility of zinc powder electrode through in-situ surface engineering towards long-life zinc-ion batteries

With the increasing popularity of aqueous zinc-ion batteries, extensive research has been dedicated to mitigating dendritic growth and parasitic reactions for zinc metal anodes. While zinc foil is currently used as a common anode, zinc powder (Zn-P) turns out to be a promising alternative. However, Zn-P is more prone to experience corrosion and induce hydrogen evolution due to its larger specific surface area, thereby resulting in poor cyclability for Zn-P-based batteries. In this study, a simple yet highly effective strategy is developed to modify Zn-P with in-situ formed indium metal protective layer that owns larger hydrogen evolution overpotential than zinc metal. The modified Zn-P is combined with nanocellulose and carbon black to form a composite electrode, which can effectively resist corrosion and hydrogen evolution, facilitate desolvation process, and promote zinc deposition kinetics. Thanks to that, the modified Zn-P realizes significantly improved cumulative zinc plating capacity of 500 mAh cm−2 during symmetric cell test and the assembled Zn//MnO2 battery achieves impressive capacity retention of 97.6% after 2000 cycles. Overall, the composite electrode not only outperforms its unmodified counterpart but also exhibits distinct advantages over previously reported Zn-P-based electrodes. This work reveals a universal pathway to modify metal powder electrodes towards high-performance batteries.

Application of Diluted Electrode Method to Sodium-ion Insertion into Hard Carbon Electrode

Herein, the diluted-electrode method is applied to a hard carbon (HC) electrode to estimate sodium-ion (Na+) insertion kinetics. As metallic nickel (Ni) particles do not accommodate Na+ ions in the potential range of 0–2.0 V vs. Na+/Na, the HC powder electrode is diluted by adding inert Ni particles, enabling the adjustment of the HC concentration while maintaining the composite electrode structure. By examining the rate capabilities of the HC electrodes with different dilutions, we confirm that the Na+ insertion rate for the highly diluted electrode is 10 times higher than that for the undiluted electrode. These improved kinetics can be attributed to the alleviation of Na+ depletion, which results in insignificant concentration polarization under dilute conditions. For a highly diluted electrode, the Na+ insertion kinetics must be controlled by the Na+ mobility in the HC particles and across the HC/electrolyte interface. Therefore, our study reveals that the inherent kinetics of Na+ insertion into HC are very high and provides a basis for developing high-power Na-ion batteries.

Characterization of Sr2Fe1,5Mo0,5O6-δ Based Solid Oxide Electrolysis Cells

Solid oxide electrolysis cells were made with (La0,6Sr0,4)0,99Co0,96Ti0,04O3-δ (LSCT) and (La0.6Sr0.4)0.95Co0.2Fe0.8O3-δ (LSCF) air electrode materials and Sr2Fe1.5Mo0.5O6-δ (SFM) and SFM/ Ce1-xGdxO2−δ (GDC) fuel electrodes. LSCF has shown significantly higher electrochemical activity when compared to LSCT electrode while at the same time LSCT has proven to be more stable. SFM/GDC fuel electrode demonstrates significant electrochemical activity in electrolysis mode when compared to pure SFM electrode. Additionally, modified method to synthesize electrode powders with different particle size distributions via spray pyrolysis method was developed.